I think that when a verbal or abstract, ironic or even a good slapstick physical sense of humour is lacking, for many viewers Jimmy being loud and annoying is what they think of as funny.
I think it's like the difference between a pie fight with great timing - which makes it funny, or on the other hand just someone chucking pies and thinking that they're a comedy genius.
Jimmy reminds me of Joe Swash. They, think they're funny so lots of other people do too. Going through the motions without actually being funny can, work - unfortunately.